Painful Phantom Limb

Blaine S. Nashold, Jr., M.D.

Phantom limb sensation following amputation is a common phenomenon. However, with the passage of time the phantom typically diminishes and causes no unusual psychic or physiologic disturbance. On the other hand, if severe pain or a long period of suffering is related to the injury, a painful phantom which defies relief by drugs or surgery may develop. Weir Mitchell's graphic account, in 1871, of the occurrence of this syndrome during the Civil War has yet to be surpassed. Unfortunately, our current therapy is little better than his.

Pain is a complex sensory modality which has two faces - one physiologic and the other psychic. At different times one or the other may predominate in a given patient, often to his distress and the physician's confusion. Pain is so personal an experience that studies in laboratory animals have yielded only limited knowledge of the phenomenon. Our most significant advances have and will come from a careful analysis of the clinical condition as it exists in man.

Sectioning the Spinothalamic Tract

Recent advances in neurosurgery have made possible improved methods of investigation, diagnosis, and treatment in cases of painful phantom. The transmission of painful impulses in the cord to higher centers of the brain such as the thalamus are poorly understood. The spinothalamic tract in the cord probably transmits most of the pain and thermal sensations, and sectioning this tract often results in the relief of pain below the level of the chordotomy. A section at the upper thoracic cord will relieve pain in the lower portion of the abdomen, pelvis, and lower extremities, but it is difficult to relieve pain that occurs in the regions of the upper extremities, head, and neck. High cervical chordotomy presents a greater surgical risk and often results in only a partial relief of pain in the arm and shoulder ([Fig. 1A ] ).

Stereotactic Neurosurgical Techniques

In 1947 Spiegel and Wycis introduced stereotactic neurosurgical techniques for the treatment of painful conditions. Using a thermal coagulation electrode, they made localized lesions in the midbrain involving the spinothalamic and quintothalamic tracts (Fig. 1B ). This procedure resulted in a complete loss of pain and thermal sensation over the opposite half of the body and relief of the painful condition. They reported marked improvement in several instances of painful phantoms involving the upper extremity.

The success of stereotactic surgical procedures depends on the precise localization of the coagulating electrode in the desired area of the brain. Anatomical localization is made by injecting air or radiopaque materials into the subarachnoid spaces to outline the ventricular system and making measurements on the roentgenographs films. Because of the anatomical variations in the brain from one individual to another, electrical stimulation of the lesion site is done prior to coagulation. The patient is usually awake, and physiological response, such as a reproduction of a sensation or pain in the limb under study, aids in the final localization. This technique has the drawback that the patient is under the duress of a surgical procedure, and the effects are not always clear-cut, nor can they be analyzed in detail.

Revised Method of Stimulation

Utilizing the original observations of Spiegel and Wycis, we have devised a method for stimulating the pain pathways in the midbrain which can be carried out with the patient fully awake and in a quiet atmosphere. Thus a careful analysis of the effects can be made and the stimulations repeated many times until a clear picture emerges of the pain from which the patient suffers. Use of this information serves to improve the anatomic localization and gives some prediction as to the success of the therapeutic lesion.

Briefly the technique is as follows: A stereotactic neurosurgical procedure is carried out in the usual manner. Several electrodes with multiple contact points are implanted through a frontal burr hole in the midbrain in the region of the spinothalamic and quintothalamic tracts. The electrode is constructed of six strands of teflon-coated stainless steel wires wrapped together to form a composite electrode 1 mm in diameter. The contact points used for electrical stimulation and EEG recordings are spaced 5 mm apart, and stimulation is applied between adjacent contacts (bipolar stimulation). The electrode can be visualized on the plain roentgenogram of the skull after it has been implanted in the brain, which makes it possible to determine its approximate anatomical location and to check against any change in position that might occur during the period of testing.

The electrodes are anchored to the scalp. When the patient has recovered from the insertion of the electrodes, a series of electrical stimulations are carried out, and each subjective and physiologic change is recorded. When the spinothalamic tract and nearby tegmental areas are activated by an electrical stimulus, pain is experienced at the periphery of the body in the area corresponding to that region of the tract. A patient can then evaluate the pain as it is produced by the electrical stimulation and compare it with his own spontaneous pain associated with the phantom limb.

To date, this technique has been used only on adults. However, there is no reason to believe that difficulty would be experienced in applying it to children.

Two persons with traumatic avulsion of the brachial plexus who developed painful phantom have been assessed by this technique. After a period of stimulation, a lesion made in the mid-

brain resulted in complete relief of their painful experiences.

Case #1--W.K.

This 29-year-old white male fell 180 feet from a tower and sustained multiple injuries, which included an avulsion of the left brachial plexus and a flaccid and senseless left arm. The patient also sustained a head injury, with loss of consciousness and confusion. When he began to recover, he complained of a burning and gripping of the fingers of the left hand.

Ten months after the injury, a left midarm amputation was carried out. Subsequently the stump was revised and arthrodesis of the shoulder performed to improve function. The phantom pain persisted, and the patient became increasingly nervous and irritable. He was referred to us by Dr. J. Leonard Goldner for possible relief of pain.

The patient entered Duke Hospital, and two chronic stimulating electrodes were introduced by stereotactic means into the right sensory thalamus and the right midbrain in the neighborhood of the spinothalamic and quintothalamic tracts contralateral to his phantom limb. For ten days stimulation was carried out while the patient was alert and cooperative, and the effects of the electrical stimulation on his phantom pain were analyzed. Stimulation of the sensory thalamus did not alter his phantom. However, stimulation of the midbrain resulted in intensification of the painful phantom. This stimulation occurred at the level of the superior colliculus and 6 mm lateral to the aqueduct of Sylvius in the region of the pain pathways.

It was decided, on the basis of these findings, to produce a lesion by heat coagulation in the region of the midbrain, from which the painful phantom could be aroused and intensified. This was done at a second stereotactic operation, and the pain and the phantom sensation disappeared immediately after the coagulation.

A loss of conjugate upward gaze was experienced due to interference of the oculomotor fibers which traverse the affected region. Some recurrence of the phantom limb sensation, but without its painful component, occurred during the following week. The patient had difficulty in localizing the position of the limb, which had been so vivid to him prior to surgery.

The patient also experienced a loss of appreciation of pin prick and thermal sensation over the left half of his face, neck, trunk, and left stump. In our experience this loss will persist and is necessary if the pain is to be permanently relieved. Some initial clumsiness of movement in the left leg has improved. The patient was discharged to his home and for the past two months has continued to have complete relief from his pain, although he is still aware of a vague phantom of the lost arm. He experienced defects in eye movements, but these usually diminish and produce no serious continuing disability. We believe that this patient's relief will be permanent, but long-term follow-up is necessary to document this opinion.

Case #2--C.B.

Two years before admission to Duke for relief of phantom limb pain, this 29-year-old white male was involved in a serious automobile accident and suffered multiple injuries, including a traumatic avulsion of the right brachial plexus. Immediately on regaining consciousness he began to complain of a severe, constant burning pain in the right elbow and hand. The right arm was flaccid and senseless. The patient required large amounts of narcotics, and drug addiction was feared.

One year after the accident, a right anterior sympathectomy from the middle cervical ganglion to the T-8 ganglion was carried out. No relief from pain was obtained, and a posterior rhizotomy of C-5 through T-l was performed, again without relief of the painful phantom.

The patient was admitted to Duke Hospital, where depth electrodes were implanted in the midbrain, and stimulations which activated and intensified his phantom pain were applied. A thermal coagulation was made in the left midbrain in the region of the spinothalamic tract, with complete relief of the painful phantom, but with loss of up ward conjugate gaze. Midarm amputation has been advised. The patient has returned to work managing his automobile agency.

When there is evidence that the lesion producing the pain extends into the central nervous system, relief of pain is best treated by interruption of the pain pathways above the level of the lesion. In the case of severe painful phantom involving the arm, the surgical technique outlined above appears to offer the best chance for relief of pain.

Blaine S. Nashold, Jr., M.D. is associated with the Department of Surgery Division of Neurosurgery Duke University Medical Center Durham, North Carolina

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Spiegel, E.A., Wycis, H.T., Marks, and Lee, A.J. "Stereotaxic Apparatus for Operations on the Human Brain," Science 106:349-350, 1947. 
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